Field of the Invention
The present invention relates to drilling tools and, more particularly to drilling tools for machining structural components made of a titanium alloy. The invention further relates to a machining process for machining structural components made of titanium alloy.
Background Information
On account of its special properties, the material titanium, or alloys thereof, is commonly used in particular, for example, in the field of aircraft construction and there for what are known as structural components, i.e., for components which in particular take on a supporting function and are exposed to certain mechanical loading. In particular, these structural components also serve for mounting rotating parts, for example axles.
Structural components of this type are manufactured as forged components and have a frame-like structure, with pockets having a pocket base which connects individual frame webs being formed between the individual frame webs. On account of the formation as a forged part, post-machining is also required after the forging in order to form the pockets in the desired geometry. Specifically, on account of the forging operation, the pockets initially have a curved surface geometry which is not precisely defined.
For machining the pockets, provision is made nowadays of a two-stage process, in which firstly a blind hole is pre-drilled by means of a flat drilling tool and then the pocket is milled out with the desired shaping with the aid of a (roughing) milling cutter, in such a manner that a flat, planar pocket base remains.
At present, the flat drilling tool used for this purpose is a modular drilling tool having support and cutting inserts fitted thereto at the end, as illustrated by way of example in FIG. 8. Here, a plurality of cutting inserts are arranged in two rows of inserts rotationally offset in relation to one another in particular by 180°. To form a flat drill, the insert cutting edges of the cutting inserts each run in a common plane in the horizontal direction, i.e., perpendicular to the axis of rotation, in order to produce a flat drilled base. The cutting inserts in each row of inserts are spaced apart from one another in the radial direction to form a gap, which is overlapped in each case by a cutting insert from the other row of inserts in the radial direction. All insert cutting edges therefore together form a common, effective cutting tooth of the flat drilling tool.
When machining such structural components made of a titanium alloy, in particular for producing the pockets, a relatively long machining time is usually required.